Welding cathode sleeves



W. SIDNEY Marc11- 10, 1942.

WELDING CATHODE S LEEVE Filed June 27, 1940 WaBon attorney welded together.

Patented Mar. 10, 1942 WELDING CATHODE SLEEVES Watson Sidney, Summit, N. J., assignor to Radio Corporation of America, a corporation of Delaware Applicatlonlune 27, 1940, Serial No 34%,621

8 @lalms. (Cl. 219-10) My invention relates to a. method of and machine for making indirectly heated cathode sleeves.

Cathode sleeves have been proposed made from flat sheet metal stock wrapped around a mandrel with the longitudi al edged portions of the sheet omrerm "seams and smooth well-shaped sleeves are difllcult loy this method. The low electrical resistance between the tightly wrapped metal sheet end its mendrei shunts most oi the welding current from the interface of the seam, and the tightly drown sheet, when heated by the welding current, pulls into the irregularities oi the mandrel and prevents withdrawal oi the mohdrel from the closed cylinder. Further, as the welding electrodes must move forward while the sheet motel is molten to per mlt hot push up oi the welding. interioces, the sheet tautehe'd on the surface oi the mandrel preventsthe necessary movement oi the motel. If the metal sheet is loosely wrapped on the mandrel to permit hot push up end allow easy removal of the sleeve from the mandrel, the sleeve cannot be accurately sized and shaped.

An object of my invention is an improved method of making a cathode deeve with e. lonsi tudinal welded seem along one side of the sleeve, which is easy to remove from-its mandrel end which does not require excessive welding cur rent.

Another object of my invention is an improved method or making welded se cathode sleeves which are easy end inexpensive to make and which are accurately sized and shaped in menuiacture.

Still another object of my invention is a mochine for making a seamed cathode that is unlures 2, 3 and 4 show in section, respectively, three principal steps in the manufacture of a cathode sleeve according to my invention, and Figure 5 is a side view of the mandrel and welding electrodes shown in section in Figures 3 and 4.

The cathode sleeve shown in Figure 1 and made according to my invention comprises a. single piece of sheet metal rolled into a round cylinder 1 and closed by a seam 2 extending longitudinally along one side of the sleeve. The edge portions or flanges 3 and 4 of the sheet metal are formed outwardly in a conventional stand-up seem, are welded together and are then laid over against the side of the cylinder. The two layers of the flanges may be extended beyond the end oi the cylinder to form a two layer integral tab 5 as shown. hosslngs t, for mice. stops, may, it desired, be pressed in thesheet motel hetero it is rolled into the cylinder.

As shown in Figure 2 the bionic is first laid over forming mandrel l, supported upon plunger and folded oy e swoge t. Plunger is then. with= drown while dies it and ii enter from each side oi the plunger to wrep the hitch mound the mandrel end to force the two edge portions of the hleni: together, as shown in Figure 3. Weld iris dies or electrodes it and ii are preferably electrically insulated in the mochine so thdt welding current may he passed through the con tactinc surfaces of the flanges ii and t, sufdcient pressure being applied to the electrodes to iorce the metal of the flanges together as the metal softens and welds. It has been found by ex perience that if the sheet is wrapped tightly around the mandrel l, as shown in Figured, icefore welding commences that imperfect welds are produced, apparently because the tight fitting; sheet on the mandrel does not permit free for= ward movement of the welding electrodes or hot push up.

I propose according to my invention to re place the iormg mandrel l with a second or welding mandrel i2 having smaller clrcumier ential dimensions than the to mandrel so that the diameter of the cylinder may be reduced without hlnding and permit free hot push up of the welding electrodes. Figure 5 shows one conventional mechanism for practicing my improved method of making welded seam cathodes. F ormlng mandrel I is shown end-to-end with welding mandrel H, the two being reclprocable through the cylinder by any convenient driving means. Hydraulic actuating means I! with a. piston rod I4 may, ior example, be connected directly to the end of mandrel I for withdrawing mandrel I after the cylinder has been formed and to bring welding mandrel l2 into the cylinder and before the welding operation is started. Reclprocatlon of the mandrels may of course be synchronized with the driving mechanism for the welding electrodes l0 and il for automatic operation. The difference in the sizes of the two mandrels l and I: will, of course, depend upon the thickness of the stock to be welded, and the desired distance I, I, M and II, while the mandrel I2' is preferably made of a high electrical resistant material such as oxidized iron or ceramic.

The diameter of the welding mandrel I2 is so chosen that as the welding electrodes arrive at the end or their travel during welding, the walls of the sleeve are drawn into snug but no binding engagement with the sides of the mandrel and are hence accurately sized and shaped so that distortions placed in the walls because of the high temperature welding will not distort the sleeve.

Alternatively, the forming mandrel I may be made collapsible, as shown in Figure 6, to the diameter of the welding mandrel 12.

My improved method of making a cathode sleeve with a longitudinally welded seam along one side of the sleeve accurately sizes and shapes the sleeve, is easy and inexpensive to practice and provides a uniform and flrmly welded seam along the side of the sleeve.

I claim:

1. The method of making a seamed sheet metal cylinder comprising the steps of wrapping a rectangular piece of sheet metal around a mandrel and forming outwardly the two longitudinal edge portions of the sheet, drawing the sheet meta cylinder into snug contact with the side 01' the mandrel to form the cylinder to the mandrel while pressing the two registering side faces 01 the outwardly extending edge portions into contact, then supporting the formed cylinder on a mandrel smaller incircmnference than the flrstmentioned mandrel, and, while pressing together said edge portions, passing welding current through said portions to heat said edge portions to welding temperature and to shrink said cylinder onto said smaller mandrel.

2. The method of making a cathode sleeve formed from a strip of sheet metal with the iongitudinal edged portions of the strip welded together, comprising wrapping a piece 01' said sheet metal around a flrst mandrel, forming or said edge portions side-by-side upstanding flanges,

holding said flanges together while removing said first mandrel from the formed cylinder and inserting a second mandrel of slightly smaller circumierential dimension than the first mentioned mandrel, and heating said flanges to melting temperature and pressing the flanges together while at said temperature.

3. A machine for making welded seam metal sleeves comprising a forming mandrel, means for wrapping a sheet metal blank around said forming mandrel and for forming upstanding flanges along the edges of the sheet parallel to the axis or the mandrel, a second mandrel or smaller circumferential size than said forming mandrel, reciprocatable welding electrodes on opposite sides of said flanges for pressing together and holding' said flanges, means to replace the first-mentioned mandrel in the sleeve with the second-mentioned mandrel while the sleeve is so held by its flanges, means for passing welding current between the electrodes through said flanges to weld togethersaid flanges while the blank is supported on the second-mentioned mandrel.

4. A machine for making a cathode sleeve with a welded seam comprising a forming mandrel of wear resistant material, a welding mandrel of electrical resistant material Joined end-to-end with the first mentioned mandrel, and means for reciprocating said mandrels.

5. A machine for making a cathode sleeve formed from a strip of sheet metal, the longitudinal edge portions of the strip being welded together, comprising a forming mandrel oi. wearresistant material about which the sheet metal is wrapped, means for forming said sheet metal snugly around said forming mandrel and for forming or said edge portions side-by-side upstanding flanges, and welding electrodes for pressing together said flanges and holding the wrapped sheet metal sleeve, a second mandrel and means for replacing the first-mentioned mandrel with said second mandrel while the flanges and sleeve are held by the electrodes, and means for passing welding current between the electrodes through the flanges while the flanges are pressed together, the circumferential size of the second mandrel being smaller than the inside size of the finished sleeve.

6. A machine for making a tubular electrode, comprising a forming mandrel about which said electrode may be wrapped, two aligned welding electrodes with extended welding surfaces parallel to the side of the forming mandrel, said electrodes being reciprocatable on a line normal to a plane through the axis of the mandrel, a welding mandrel slightly smaller in circumferential dimension than the first-mentioned mandrel and joined end-to-end with said first-mentioned mandrel, and means for reciprocating said mandrels and said electrodes in synchronism.

7. The method of making a cathode sleeve from Y a strip or sheet metal comprising snugly wrappingthe sheet around a mandrel, forming upstanding side-by-side flanges along the longitudinal edges of the sheet, pressing said flanges together to hold said flanges and the formed sleeve while replacing the first-mentioned mandrel with a second mandrel of slightly smaller diameter than said formed sleeve, and then, while the flanges are pressed together, passing welding current through the flanges.

8. The method or making a cylinder from a strip of sheet metal with edge portions of the strip longitudinally of the cylinder welded together, comprising wrapping a piece of sheet metal around a mandrel and forming said sheet to the contour of the surface of said mandrel, and forming the edge portions of the sheet into side-by-side upstanding flanges longitudinally of the mandrel, the flanges being in contact while the cylinder and mandrel are in contact, then relieving th pressure between the cylinder and mandrel, and then passing welding current transversely through the contacting flanges while the flanges are pressed together,

WATSON SIDNEY. 

